Exhaust brakes are known for over-the-highway trucks and similar vehicles. Such vehicles are generally powered by an internal combustion engine, often a diesel engine. Such engines displace exhaust under substantial pressure. If obstruction to displacement of exhaust is provided, the engine will operate less efficiently. Thus, blockage of exhaust flow tends to slow engine operation and act as a brake. For example, through utilization of an appropriate system to block exhaust flow from the truck engine, a truck driver can slow down the vehicle with less wear and strain on the braking system for the wheels.
A variety of conventional exhaust brakes are known. In general these comprise valves that place a restriction, for example a restricted orifice, of fixed size into or out of alignment with exhaust gas flow. The restriction provides a smaller passageway for the exhaust gases, and thus inhibits exhaust flow. This creates a back pressure, providing the braking action. Generally these systems are designed so that the maximum back pressure provided is within safe operating limits for the engine, to reduce risk of engine damage.
As the vehicle slows down, the engine output and exhaust output begin to slow down as well. Thus, the back pressure or braking action provided by the exhaust brake reduces in time. Typically a vehicle operator will down shift throughout the braking action, each down shift reestablishing a higher engine rate and thus increasing exhaust flow. The increase in exhaust flow which accompanies each down shift will provide renewal of back pressure and thus regenerate braking action if the exhaust brake is in position.
The typical exhaust brake is operated with an overriding on/off switch in conjunction with a throttle-activated switch. The controls are configured so that removing pressure on the throttle automatically triggers the exhaust brake switch, restricting the orifice and slowing down the engine. In some systems automatic operation is replaced with a manual control that is operated to restrict exhaust flow (or remove restriction of exhaust flow) at the selection of the operator.
Typically the exhaust brake is located at or near the exhaust manifold for the engine. Thus, it is near the source of exhaust.
It is a purpose of the present invention to provide for improved exhaust brake arrangements.